Difference Between Diffusion and Osmosis

Diffusion vs Osmosis

Diffusion and Osmosis are physical processes that are often confused with one another and people find it difficult to differentiate between the two. These are processes that are found in nature and are related with movement of atoms and molecules from areas of higher concentration to areas of lower concentration. These are concepts that are normally taught in physics, chemistry and also biology and hold great significance in science. All processes in nature are explained on the basis of movement of atoms and molecules and these two concepts beautifully sum up all these processes at a microscopic level.

Having said that both diffusion and osmosis involve movement of molecules, how do both compare with each other and what are the basis differences between the two concepts. While diffusion involves movement of any chemical from one place to another, osmosis involves movement of only water across a permeable membrane. This makes it clear that it is only water that can undergo osmosis. As such it can be said that osmosis is a special type of diffusion. A practical example of osmosis is when we feel thirsty after eating something salty as this salt draws water from cells of the body.

Diffusion takes place without a membrane whereas osmosis takes place across a semi permeable membrane only.

In the case of diffusion molecules can flow in any direction, while in osmosis, the flow of molecules is in one direction only.

Diffusion as a process is not confined to liquids and even gases diffuse. One good example of gaseous diffusion is room spray which is felt at the other corner of the room. Osmosis can only take place in solutions that are aqueous in nature.

Osmosis is slower in nature while diffusion takes place at a faster rate.

Diffusion takes place over both short as well as long distances whereas osmosis can take place over short distances only.

Diffusion is not dependent upon water for flow of molecules, while osmosis takes place only in water.

One similarity between osmosis and diffusion is that they are both passive in nature and no external force is required for the flow of molecules from one place to another. Both diffusion and osmosis play a great role in living organisms to achieve a state of equilibrium inside. In the case of plants, osmosis is necessary for cell membranes to absorb water and other liquids, while diffusion allows water, oxygen and carbon dioxide to pass through. In case of animals (including humans), osmosis is more important as it allows for distribution of nutrients and release of waste products.


Both diffusion and osmosis involve movement of molecules from areas of high concentration to areas of low concentration.

While diffusion takes place through solid, liquid and gases, osmosis take place only in water.

Osmosis is a special type of diffusion

Diffusion can take place across all distances, while osmosis take place across permeable membrane over a short distance.

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  • sana cool

    tell me difference between osmosis and diffusion